1. Field of the Invention
This invention relates to a gas-turbine engine combustor.
2. Description of the Related Art
As taught for example by Japanese Laid-open Patent Application No. Hei 4(1992)-43220, one known type of gas-turbine engine combustor, more specifically premixed combustor, uses fuel injection nozzles distributed before and after the swirl to premix fuel and air by swirling.
Another type, such as that taught by Japanese Laid-Open Patent Application No. Hei 7(1995)-248118, uses fuel injection nozzles provided at the inlet portion of multiple premixing pipes to premix fuel and air without swirling or has premixing pipes disposed in the combustion chamber so as to produce a swirling flow.
Still another type, such as taught by Japanese Laid-Open Patent Application No. Hei 1(1989)-163426 (corresponding to U.S. Pat. No. 4,845,952), uses multiple venturi mixers (a multi-venturi mixer) to supply a homogeneous or uniform premixing to the combustion chamber and reduces NOx by passing the combusted gas through a downstream catalyst bed.
The technology taught by Publication No. 4(1992)-43220 is disadvantageous in that it produces a circulating and/or reverse flow and, moreover, is readily affected by the resulting wake to self-ignite or backfire.
In the case of the technology taught by Publication No. 7(1995)-248118, when the premixing pipes are long, self-ignition is apt to occur and it is difficult to obtain a homogeneous or uniform air-fuel mixture. The technology taught by Publication No. 1(1989)-163426 requires installation of a swirler downstream of the mixer in the case of lean premixed combustion, but the installed swirler increases the likelihood of backfire and self-ignition.
Thus, these prior art technologies cannot easily generate a homogeneous or uniform air-fuel premixing (i.e., a homogeneous fuel distribution) without producing backfire and/or self-ignition and are also incapable of readily achieving stable lean premixed combustion. They therefore leave much to be desired from the aspect of further decreasing emissions by expanding the premixed combustion range.
An object of the present invention is therefore to overcome the foregoing shortcomings by providing a gas-turbine engine combustor that does not produce backfire or self-ignition, that produces a highly homogeneous air-fuel premixing, and achieves stable lean premixed combustion, thereby expanding the premixed combustion range to realize further reducing of emissions.
The present invention achieves the foregoing object by providing a gas-turbine engine combustor having a plurality of venturi mixers, each connected to an air supply path that passes air compressed by a compressor and to a supply source of gaseous fuel, which mix the air and the gaseous fuel to produce an air-fuel mixture and supply the air-fuel mixture to a combustion chamber for combustion such that produced combustion gas rotates a turbine that outputs its rotation through an output shaft, while driving the compressor by the rotation; including: an air inlet formed in each of the venturi mixers and connecting to the air supply path; a fuel inlet formed in each of the venturi mixers and connecting to the supply source of gaseous fuel; an air-fuel mixture generating passage, formed in each of the venturi mixtures, which connects to the air inlet and the fuel inlet and merges with an air-fuel mixture generating section to produce the air-fuel mixture; and a nozzle or jet which opens into the combustion chamber at an end of the air-fuel mixture generating passage; wherein the venturi mixers are arranged radially around a center axis of the combustion chamber; the air-fuel mixture generating passage formed in each of the venturi mixers is provided with a throttle section of diminishing diameter; and the nozzle or jet is shifted circumferentially about the center axis relative to the air inlet such that the air-fuel mixture generating passage is deflected in a circumferential direction between the throttle sections and the nozzle or jet.